Hannover 2003 – wissenschaftliches Programm
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Q: Quantenoptik
Q 3: Laserspektroskopie 1
Q 3.6: Vortrag
Montag, 24. März 2003, 12:15–12:30, F107
Photodegradation of Chlorosome Bacteriochlorophylls of Chlorobium tepidum — •Anton Granzhan1, Alfons Penzkofer1, and Guenter Hauska2 — 1Institut II - Experimentelle und Angewandte Physik, Universität Regensburg, Universitätsstrasse 31, D-93053 Regensburg — 2Institut für Botanik, Universität Regensburg, Universitätsstrasse 31, D-93053 Regensburg
The photostability of bacterichlorophylls (BChl, mainly bacteriochlorophyll c) is studied by cw light excitation in the chlorosomes of intact green sulfur bacteria Chlorobium tepidum and in extracted solutions where BChl is present in monomeric form. Experiments have been carried out under aerobic and anaerobic conditions. The photostability of BChlc in the chlorosomes is very high (quantum yield of photo-degradation φD ≈ 7.5 ×10−6 ) under both conditions. The BChl molecules in acetone/methanol solution have low photo-stability in air-saturated samples ( φD ≈ 0.017 ). The photo-stability increases by nitrogen bubbling. The photo-degradation is caused by reaction of BChls with dissolved oxygen after excitation. Singlet excited BChls relax partly to the triplet system and react with triplet oxygen to generate singlet oxygen and ground-state BChl. The generated singlet oxygen reacts with BChl to a peroxide BChl-O2 which degrades thermally to photobiline and further to products not absorbing in the visible spectral range.